Aryldiazonium ion reagents are widely employed in clinical chemistry and histochemistry for the detection and determination of biological substances. Because of low thermal stability, the arenediazonium salts are prepared in situ by diazotization of arylamines under carefully controlled conditions and are used shortly thereafter. Recently, we have demonstrated that complexes of synthetic ionophores and aryldiazonium salts possess markedly enhanced thermal and photochemical stability relative to the corresponding uncomplexed arenediazonium salts. In the proposed research, the stability of one-to-one ionophore-diazonium salt complexes will be assessed in order to determine if these complexes may be used as "off the shelf" diazonium ion reagents for biological analyses. Effects of aromatic ring substituents, diazonium counterion, ionophore, temperature, and atmosphere upon complex stability will be measured.